The present invention relates to baluns. More specifically, the present invention relates to baluns fabricated on substrates.
Baluns, also known as transformers, are used for transmitters and receivers. The baluns convert differential ports to single ended ports and vice versa. A given balun operates over a band of frequencies.
Originally, cellular telephones operated in a single regime (analog) and in one frequency band, using a single balun for transmission or reception. More recently, cellular telephones operate in multiple regimes or bands, such as operation in the cellular and PCS bands or quad-band phones for operation pursuant to multiple US and European standards.
Multiple baluns may be used for different frequency bands of operation. Where the baluns are wound wire or multi-layer ceramic devices, each extra balun consumes extra space and/or increases cost. This is disadvantageous in portable electronic devices continually required to either be reduced in size or increased in functionality while maintaining the same size.
Space may be saved by integrating a balun on a substrate. However, separate baluns and corresponding chips for different frequency bands are provided to avoid signal loss and interference. Separate baluns may still consume space and increase cost.